This invention relates wastewater treatment systems in particular systems and methods for dealing with wastewater runoff which may contain hydrocarbons such as may be found in a car wash, or auto fueling area.
Wastewater treatment is a well-known area and there are numerous systems for treating area runoff including such systems as U.S. Pat. Nos. 5,707,527 and 6,080,307. These systems are designed to work with large scale centralized storm water drain systems or are complex highly mechanized systems which are cost prohibitive and require regular maintenance.
However, there are many instances where hydrocarbon accumulation is highly localized. Such locations may consist of a limited area water impermeable surface that receives occasional hydrocarbon contamination. Areas such as auto fueling stations and car wash areas produce localized concentrations of runoff that should be treated prior to discharge into a general wastewater system or gray water reclamation system. Often there are regulations by local and regional governmental bodies that require local and private treatment of water runoff.
The present invention meets the need to provide a device for treating localized contaminated runoff. The device provides an inexpensive, low maintenance and versatile method and device for treating contaminated runoff, which is easily installed to service new development, and existing locations.
The invention provides an apparatus and treatment method for wastewater runoff to remove hydrocarbons and other contaminants from wastewater prior to discharge into a general wastewater system. The invention may also be adapted to treat wastewater for collection as gray water for reuse. The invention consists of a self-contained canister with a water inlet disposed on one side, and a series of vertical hydrophobic filter units through which the water must pass. The invention is also adaptable to be placed in series with pre-chamber settling or storage tank to collect sudden large volume accumulation and avoid exceeding unit capacity.
In the preferred embodiment, preceding the first filter unit is a settling area to reduce turbidity and allow larger particles to settle prior to impacting the first filter. Following thereafter are a series of vertical filters. Between each vertical filter are additional settling areas. In the preferred embodiment there are at least three vertical filters for collection of hydrocarbons and particulate material.
While there are advantages to multiple grades and types of filter material, economics and ease of maintenance and use often calls for a single coarser material to be used in series. Over time the first filer unit will reach filtering capacity and become effectively plugged. When the first filter reaches capacity, water in the first settling area will overflow and be filtered by the second filter unit, reducing the over all effectiveness of the invention, but still leaving processed water in an acceptable condition for discharge or reuse.
In the preferred embodiment, the series of filer units are placed on a grade of 2% or more to give the water a natural flow from the water inlet through the filter units.
After the last filter unit, a separator disposed so as to permit heavy non-filtered contaminants to settle and light non-filtered contaminants to collect on the surface of the water. Contaminants are removed from the separator with the regular filter maintenance of the unit in addition to processes such as natural breakdown and evaporation.
The separator is comprised of a first separator tank disposed to contain a significant volume of water below the level of the last filter. This serves a number of purposes. As the tank drains, the filter units are exposed to air and allowed to dry, extending their life. This lower reservoir is also used to collect additional particulate matter and to provide a water substrate for oil to collect and be kept above a lift tube that drains this reservoir into the final separator tank.
The lift tube is placed in the separator tank so as to be below the surface of the water level and to collect the water and lift it via siphon or pump into the second separator tank for a final settling. In the preferred embodiment, a float type switch activates the pump. The lift tube discharges the water from the first separator tank into the second reservoir in a manner that prevents excessive agitation of the water in the second separator tank, and in the preferred embodiment, as a sprayed sheet along one of the walls in the second separator tank.
An outlet is located medially in a wall of the second separator tank. In the preferred embodiment, water is neither drained off the top, nor the bottom of this tank. This permits settled matter to remain undisturbed on the bottom of the tank and to permit further hydrocarbon accumulation on the surface of the water. The water outlet then drains to a general wastewater system or a gray water reclamation system for reuse.
In normal use, the filter units will become clogged over time depending on the volume of water processed and the amount of contamination. The simple layout of the device provides for easy regular access to the filters for maintenance.
The entire device is accessible through the top of the unit and necessary maintenance is quickly accomplished. Filter units may be replaced in whole, or they may be left with open or removable tops to permit the contents to be vacuumed out and refilled with loose filter medium. A simple vacuum sweep with or without accompanying wash of the settling tanks and the reservoirs removes any build up of contamination.
There are many filter materials available of varying degrees of utility. In the preferred embodiment, a basic cellulose pulp is used, as it is a cheap and plentiful byproduct of the timber industry. When the filter medium is fully exhausted, cellulose pulp is easily vacuumed and in high demand as a fuel for co-generation waste incinerators, burning relatively cleanly.
The open nature of the device permits use of multiple filter mediums in whole or series. The devise is readily adaptable to accommodate inexpensive loose cellulose filter material in one or more of the first filers and a carbon or charcoal medium in one of the later filters. Use of a carbon or similar medium in a later stage filer aids in the removal of odors and silicon wax based contaminants which are common in many car washes.
Other options include using bagged filter material that may be placed in the filter canisters and sheet filter material inserted into the canisters or even between canisters. Bags of filter material may either be such that a single bag is placed in each canister or multiple bags may be placed in a single canister. This permits less expensive material to be exhausted rapidly in the earlier filters, and still provides filtering with more expensive though more specific filter mediums in a later stage.
The device also permits the change of the filter mediums to fit the needs of a location that may experience specific contamination depending on the season. Wintertime loads in many areas have distinct contamination components that may not be present during warmer months permitting insertion of a specific filter medium to isolate and collect these contaminants.